This application seeks to expand and refine a new reaction for the preparation of highly substituted pyridines, in connection with the total synthesis of marine alkaloids with pronounced cytotoxic activity. The new reaction is extremely efficient, and it produces pyridines by a two-step process involving inverse-demand Diels-Alder reaction of an enone (or an enal) with a vinyl ether, followed by treatment of the adduct with hydroxylamine hydrochloride (80-90 % yield of pyridine overall). This chemistry has already been employed in the total synthesis of cystodytins and lavendamycin. Both compounds are of interest as candidate antitumor agents, especially the cystodytins, which by virtue of their novel structure represent interesting new leads in cancer chemotherapy.